Adjustment of structural and optical features of nanocomposite based on polyvinyl butyral film with antimony oxide for UV shielding and optoelectronics‏

Abstract

In this paper, transparent polyvinyl butyral/antimony oxide (PVB/Sb₂O₃) nanocomposites with good UV shielding effectiveness are prepared. Solution casting was used to produce PVB/Sb₂O₃ nanocomposites with different Sb₂O₃ percentages. XRD and FTIR confirmed the interaction between PVB and Sb₂O₃. SEM and EDS mapping revealed that Sb₂O₃ nanoparticles with an irregular polygonal structure have a Sb/O ratio of ∼0.44. The integration of Sb₂O₃ resulted in a measurable alteration in PVB’s linear and nonlinear optical characteristics. For example, the reduction in transmittance of PVB was detected upon increasing the nanofiller content. Increasing the Sb₂O₃ ratio resulted in a reduction of the energy band gap of PVB, attributed to changes in localized energy states and defect levels within the host PVB’s band gap. Increasing the amount of Sb₂O₃ causes a rise in the refractive index, dispersion energy, static refractive index, and dielectric constant of nanocomposites. The results show that Sb₂O₃ can alter the optical properties of PVB, enabling it to be utilized in various applications, including UV protection, optical cables, anti-reflective films, and optoelectronic devices.

Introduction

Polymer nanocomposites are essential in the discovery of innovative products utilized in various technological applications.^1–4 The polymer nanocomposites predominantly comprise a polymeric medium infused with nanofillers of low aspect ratios. Nanofillers, derived from both organic and inorganic materials, have numerous applications in various fields, including energy storage, radiation shielding, optoelectronics, photocatalysis, quantum nanoelectronics, and biomedical engineering.^5–14

Among diverse polymeric materials, polyvinyl butyral (PVB) is regarded as a compelling candidate for the fabrication of polymer nanocomposites across various applications owing to its flexible molecular structure, low glass-transition temperature, superior binding strength, high optical clarity, exceptional mechanical strength, favorable biocompatibility, hydrophilic characteristics, and significant adhesive properties with glass and metal.^5,15 PVB was used to increase the stability of copper and nickel-based electromagnetic shielding fabrics. ¹⁶ A composite made from PVB and mica flakes was used as an effective barrier coating to protect organic solar cells protected against photobleaching made of poly (3-hexylthiophene). ¹⁷

Polymer composites may benefit from the addition of metal oxide nanoparticles due to these particles’ remarkable optical and antibacterial properties, as well as their enhanced mechanical strength, chemical resistance, and thermal stability. Their tiny stature and large surface area give them unique characteristics. ¹⁸

Antimony oxide (Sb₂O₃) is classified as a heavy metal oxide and has a high refractive index, excellent photothermal behavior, and transparency to infrared light. Additionally, Sb₂O₃ contributes to the semiconductor industry. ¹⁹ Furthermore, Sb₂O₃ has a large and direct band gap in the near-ultraviolet region, which is beneficial for high-efficiency flame-retardant and UV shielding applications. ²⁰

PVDF-CTFE fibrous membrane was modified with Sb₂O₃ for lithium-ion batteries. A small amount of Sb₂O₃ enhanced the mechanical, flame retardancy, and thermal stability of PVDF-CTFE. ²¹

An improvement in tensile strength, resistance of water vapor permeability, and UV absorbance of glycerol-plasticized starch by Sb₂O₃ nanoparticles prepared via carboxymethyl cellulose sodium as stabilizing agent was reported. ²⁰

The solution casting technique has several advantages, particularly the capacity to control film thickness and its ease of use at the laboratory level. This technique faces numerous challenges that restrict large-scale production, such as excessive organic solvent usage, prolonged manufacturing duration, and the nonhomogeneous distribution of fillers within the polymer matrix. ²²

In this work, the impact of Sb₂O₃ on the structural and linear/nonlinear optical features of PVB was studied for the first time. The PVB/Sb₂O₃ nanocomposites were synthesized by the solution casting method. Different PVB/Sb₂O₃ nanocomposites were prepared by incorporating different small ratios of Sb₂O₃ (1, 2, and 3 wt%) into the PVB host polymer. The samples’ characterization was performed via XRD, FTIR, SEM, EDX, and UV-Vis spectroscopy. The investigation will focus on the behavior of structural, linear, and nonlinear optical characteristics, including the optical energy gap, optical susceptibility, dispersion energy, linear refractive index, and oscillator strength of various nanocomposites.

Experimental

Perpetration of PVB/Sb₂O₃ nanocomposites

Antimony (III) oxide (Sb₂O₃) powder and PVB were purchased from Sigma-Aldrich. The PVB/Sb₂O₃ nanocomposites were fabricated by dissolving 0.2 g of PVB in 5 mL of alcohol. Magnetic agitation was used to stir the solution at the surrounding temperature for 20 min to ensure homogeneity. The PVB solution was doped with Sb₂O₃ at variable concentrations (0, 1, 2, and 3) wt%. The solution casting procedure adhered the resultant solutions to glass substrates. The PVB/Sb₂O₃ nanocomposites were cured for 2 days at ambient temperature. The thickness of the nanocomposites was measured using a digital thickness Gauge (approximately 700 ± 20 μm).

Characterization techniques

The XRD pattern of PVB/Sb2O3 was measured using the D8 Bruker with the X-ray generator using the Cu-Kα, λ= 1.54 Å. The FTIR spectrometer, a Bruker Alpha, was successfully used to acquire FTIR spectra. SEM and EDX (Zeiss) were used to determine surface morphology and elemental composition. The UV–Visible spectrophotometer (operating from 190 to 2500 nm) was used to measure the spectra of absorbance and reflection.

Results and discussion

SEM and EDS of Sb₂O₃ nanoparticles

The morphology and composition of pristine Sb₂O₃ nanoparticles used in this work were surveyed by SEM and EDS. As revealed in SEM images (see Figure 1(a)), Sb₂O₃ exhibits an irregular polygon structure with different sizes.

Figure 1.

SEM image at high and low magnification (a), SEM and its corresponding EDS mapping (b), EDS profile of Sb₂O₃ nanoparticles (c).

Figure 1(b) shows the low magnification SEM picture and EDS elemental mapping of the specimen. Sb₂O₃ contains O and Sb, which are evenly distributed across the surface of the product.

Figure 1(c) provides evidence of a typical Sb₂O₃ EDS pattern. The Sb and O peaks are readily apparent. ²³ Quantitative EDS analysis also shows that antimony and oxygen have atomic composition values of around 30.66% and 69.3%, respectively. This indicates that the atomic ratio of Sb to O is 0.44.

XRD

XRD patterns of pure PVB and Sb₂O₃ are presented in Figure 2. The XRD of pure Sb₂O₃ show peaks at 19.02°, 25.17°, 28.11°, 32.65°, 33.57°, 36.2°, 43.94°, 46.79°, 50.3°, 54.5°, 58.6°, 60.57°, and 66.5° which corresponded to (1 1 0), (1 1 1), (1 2 1), (0 0 2), (0 1 2), (2 0 0), (0 4 2), (2 4 0), (1 6 1), (1 7 0), (2 4 2), (0 7 2), and (2 7 1) planes which well consistent with orthorhombic Sb₂O₃, the peaks were well consistent with JCPDS card No. 11-0689. ²⁴ Pristine PVB exhibits a large, broad, and intense diffraction peak at 2θ = 19.42^o with an interplanar spacing of 0.46 nm. It is attributable to a polymer’s amorphous phase. ²⁵ Upon inclusion of Sb₂O₃ into the PVB, both diffraction peaks of PVB and Sb₂O₃ were observed. As well as, the peak intensity of PVB is decreased upon increasing Sb₂O₃ concentration. This behavior indicates that the interaction of filler with PVB leads to an increase in the crystallinity of nanocomposites. ⁷

Figure 2.

XRD of Sb₂O₃ and different PVB-Sb₂O₃ nanocomposites.

FTIR

FTIR of pure PVB and PVB/Sb₂O₃ nanocomposite is presented in Figure 3. The pure PVB film shows a small peak at 3399 cm⁻¹ assigned to hydroxyl groups. Additionally, the 2885–2938 cm⁻¹ are attributed to saturated CH, CH₂, and CH₃ stretching vibrations. The peaks at 1425 cm⁻¹, 1373 cm⁻¹ and 1345 cm⁻¹ are assigned to C–H bending vibrations. The peak at 1133 cm⁻¹ is assumed to be due to C–O–C–O–C stretching vibrations of cyclic acetal groups. The small peak at 1729 cm⁻¹ pertains to C−O stretching vibration of the acetate group. The peaks at 984 cm⁻¹ and 1242 cm⁻¹ are attributed to C–O–C stretching vibration of acetate group.^26,27 Upon incorporation of Sb₂O₃ into PVB, the intensity and broadening of hydroxyl group and CH and CH₂ groups are observed. Furthermore, the increasing intensity of the transmission band in region 1000–15,000 was observed. This indicates there is a strong interaction between PVB and Sb₂O₃. ²⁸ There is a possibility that hydrogen bonds were formed between the PVB chains and the oxygen atoms in the surface of the Sb₂O₃ nanoparticles. ²⁹

Figure 3.

FTIR of PVB and different PVB-Sb₂O₃ nanocomposites.

Optical properties

Figure 4(a) elucidates the variation of absorbance (A) versus wavelength (λ) for PVB/Sb₂O₃ nanocomposites. The incorporation of Sb₂O₃ NPs into polyvinyl butyral (PVB) films enhances their absorbance properties. The previous spectral line exhibits a redshift accompanied by an additional broadening effect. Furthermore, a distinct redshift in the cut-off edges is observed, ranging from 242 nm (for the PVB) to 255 nm (for the PVB/3 wt%Sb₂O₃) nanocomposite. Clearly, the transmittance (T) spectra of the PVB/Sb₂O₃ nanocomposites declined as the Sb₂O₃ NPs concentration increased. For instance, the T quantity decreased from 88% (PVB) to 21% (PVB/3 wt%Sb₂O₃ nanocomposite), as illustrated in Figure 4(b). The reduction in T and termination of edges redshift suggests the contraction of optical bandgap of the PVB/Sb₂O₃ nanocomposites as a consequence of a rise in the Sb₂O₃ NPs concentration. The evaluation of optical transmittance demonstrates the capacity to modulate the transmittance of the PVB/Sb₂O₃ nanocomposites through the incorporation of Sb₂O₃ NPs nanostructures. This novel result advocates for the utilization of PVB/Sb₂O₃ nanocomposites in applications involving UV-spectrum filters. ³⁰ The reflectance (R) measurements (Figure 4(a)) suggest that the behavior of the PVB/Sb₂O₃ nanocomposites is depends upon the quantity of Sb₂O₃ NPs. The packaging density of the PVB/Sb₂O₃ nanocomposites can be altered by doping, which then affects their reflectance properties and, as a result, R values. ³¹

Figure 4.

(a) The variation in A, (b) T, and (c) R spectra versus λ for PVB/Sb₂O₃ nanocomposites.

The optical absorption coefficient (α cm⁻¹) versus the energy of incident photons (hv) for PVB/Sb₂O₃ nanocomposites was determined using next equation ³² and is depicted in Figure 5.

$\mathit{\alpha }=\frac{\mathbf{1}}{\mathit{d}}\mathit{ln}\hspace{0.17em}\left(\frac{{\left(\mathbf{1}-\mathit{R}\right)}^{\mathbf{2}}}{\mathit{T}}\right)$

(1)

Figure 5.

Absorption coefficient (α cm⁻¹) versus hv for PVB/Sb₂O₃ nanocomposites.

The thickness of the film is represented by the variable (d).

It is evident that α exhibited a progressive increase with the rise of hv within the visible to near-infrared (NIR) spectrum. Also it showed a significant increase in ultraviolet region. Additionally, it is noted that the absorption edges of the PVB/Sb₂O₃ nanocomposites shift towards lower hυ as the percentage of Sb₂O₃ NPs increases. Our findings demonstrate a decrease in optical bandgap values of the PVB/Sb₂O₃ nanocomposites resulting from doping with Sb₂O₃ nanoparticles.

The optical bandgap of the PVB/Sb₂O₃ nanocomposites can additionally be obtained by applying Tauc’s relation ³³ :

$\mathit{\alpha }\mathit{h}\mathit{\nu }={\mathit{A}\left(\mathit{h}\mathit{\nu }–{\mathit{E}}_{\mathit{g}}\right)}^{\mathit{s}}$

(2)

The symbols for photon frequency (υ), Planck constant (h), proportionality constant (A), and electronic transition index (s) are used.

To ascertain the direct optical band gap (E_g) of the PVB/Sb₂O₃ nanocomposites, plots of (αhv)² against hν were generated, as illustrated in Figure 6. The E_g values have been identified by extrapolating the linear sections of the plotted curves to the point where hν equals zero.^34–36 Table 1 presents the estimated E_g values. It can be observed that the E_g1 and E_g2 values of the blank PVB are 5.10 eV and 5.28 eV, respectively. On the other hand, the E_g1 and E_g2 of the PVB/Sb₂O₃ nanocomposites diminish when the Sb₂O₃ nanostructures are doped to 4.72 eV and 4.88 eV, respectively, for the 3 wt% Sb₂O₃ doping. Sudarat Kumsaart et al. ³⁷ have synthesized polyethylene glycol with various Nb₂O₅ and CaBr₂⋅xH₂O concentrations. They reported that the band gap values of the polymer layers go down from 3.0 eV to 2.06 eV.

Figure 6.

Plots of (αhv)² against hν of the PVB/Sb₂O₃ nanocomposites.

Table 1.

The values of E_g and E_u, for PVB/Sb₂O₃ nanocomposites.

Sample	Eg (eV)		Eu (eV)
	Eg1	Eg2
PVB +0% Sb2O3	4.10	5.28	1.57
PVB +1% Sb2O3	3.94	5.13	2.73
PVB +2% Sb2O3	3.84	5.01	3.21
PVB +3% Sb2O3	3.72	4.88	4.10

The decrease in E_g of the PVB/Sb₂O₃ nanocomposites is mostly due to the Sb₂O₃ NPs, which notably alter the structure of PVB. The adjustments are achieved by modifying the amounts of defects and localized energy states within the bandgap of the PVB. The inclusion of Sb₂O₃ NPs in the PVB induces significant structural disorder, resulting in a notable alteration of its overall physical characteristics.^30,38 The disorder level and defect ratios in PVB and PVB/Sb₂O₃ nanocomposites may be examined by analyzing the Urbach energy (E_U). The E_U of the blank PVB and PVB/Sb₂O₃ nanocomposites is ascertained based on the empirical methodology delineated in formula ³⁹ :

$\mathit{\alpha }={\mathit{\alpha }}_{\mathbf{0}}\hspace{0.17em}\mathit{exp}\left(\raisebox{1ex}{$\mathit{h}\mathit{\nu }$}\!\left/ \!\raisebox{-1ex}{${\mathit{E}}_{\mathit{U}}$}\right.\right)$

(3)

The E_U corresponds to the reciprocals of the slopes of the ln α versus hv plots, as seen in Figure 7. The identified E_U values are shown in Table 1. Significantly, the E_U value of the blank PVB is 1.57 eV. The E_U value of the blank PVB increases to 4.1 eV with the addition of Sb₂O₃ NPs. This data indicates the rise in defect levels and localized states inside the bandgap of the host PVB.

Figure 7.

Urbach energy assessment of the PVB/Sb₂O₃ nanocomposites.

Furthermore, the coefficient of extension (k) ( $\mathit{k}=\frac{\mathit{\alpha }\mathit{\lambda }}{\mathbf{4}\mathit{\pi }}$ ) elucidates the process of distinguishing a material for a particular wavelength of light. It demonstrates the variations in absorption arising when an electromagnetic wave travels through an optical material. ⁴⁰ The correlation between k and hυ is illustrated in Figure 8. It is evident from this Figure that the k enhances as the content of Sb₂O₃ NPs rises as a consequence of the electromagnetic waves scattering phenomenon.

Figure 8.

The correlation between k and hυ for the PVB/Sb₂O₃ nanocomposites.

Additionally, the refractive index (n) is a critical element of various optical parameters that must be identified to recommend its suitability for use in optical device technologies. The refractive index investigation provides insight into the behavior of electromagnetic waves as they traverse the optical material. ³⁰ The n values of the PVB/Sb₂O₃ nanocomposites were determined by utilizing the following expressions^41–43:

$\mathit{n}=\frac{\mathit{1}+\mathit{R}}{\mathit{1}‐\mathit{R}}+\sqrt{\frac{\mathit{4}\mathit{R}}{{\left(\mathit{1}‐\mathit{R}\right)}^{\mathit{2}}}–{\mathit{k}}^{\mathit{2}}\hspace{0.17em}}$

(4)

The n curves of pure PVB and PVB/Sb₂O₃ films are illustrated in Figure 9. The incorporation of Sb₂O₃ NPs results in an upsurge in the values of the n. As the concentration of Sb₂O₃ NPs rises the density of packaging improves which can be attributed to modifications to the PVB matrix. Additionally, the quantity of unrestricted carriers and the degree of reflection in the PVB/Sb₂O₃ nanocomposite films grow as the concentration of Sb₂O₃ in the PVB/Sb₂O₃ nanocomposite films increases. Consequently, the refractive index increases as well. The comparable features have been observed in PEO/PVA/MWCNTs/ZnO nanocomposites. ⁴⁰

Figure 9.

The refractive index (n) spectra of the PVB/Sb₂O₃ nanocomposites.

The increased refractive index of PVB/Sb₂O₃ makes it suitable for enhancing the functionality of applications in optical waveguides, optical fibers, anti-reflective coatings, and optoelectronics.

Additionally, the optical dispersion parameters are among the most critical parameters in the field of applications involving optical electronics. The Wemple–DiDomenico (WDD) single-oscillator model is employed for computing these parameters, which is denoted as ⁴⁴ :

$\frac{\mathit{1}}{{\mathit{n}}^{\mathit{2}}–\mathit{1}}=\frac{{\mathit{E}}_{\mathit{o}}}{{\mathit{E}}_{\mathit{d}}}–\frac{\mathit{1}}{{\mathit{E}}_{\mathit{O}}\hspace{0.17em}{\mathit{E}}_{\mathit{d}}}{\left(\mathit{h}\mathit{\nu }\right)}^{\mathit{2}}$

(5)

The static refractive index values (n_o) of PVB/Sb₂O₃ nanocomposites at frequency is zero (hv→0) ⁴⁵ :

${\mathbf{n}}_{\mathit{o}}={\left(\mathbf{1}+\frac{{\mathit{E}}_{\mathit{d}}}{{\mathit{E}}_{\mathit{o}}}\right)}^{\mathbf{1}/\mathbf{2}}$

(6)

The static dielectric constant (ε_s) may be obtained by using the static refractive index ε_s= n_o². ⁴⁶ Where E_d represents the dispersion energy and E₀ represents the average excitation energy of electronic transitions (oscillator energy). The relationship between (n² – 1)⁻¹ and (hυ)² has been shown in Figure 10. This relationship is represented by a linear line. Table 2 displays the calculated values. It is evident from Table 2 that the concentration of Sb₂O₃ in the PVB matrix leads to an increase in the values of E_d, n₀, and ε_s. The values of E_d increased significantly from 3.53 to 5.36 eV, and n_o enhanced from 1.340 to 1.606, while ε_s, rose from 1.80 to 2.58, while the E₀ values declined from 4.41 to 3.39 eV for PVB/3 wt%Sb₂O₃ film. This suggests that the charge transfer between the Sb₂O₃ and the PVB macromolecules has been rising, alongside the degree of disorder in the PVB structure. ⁴⁷

Figure 10.

Variation of (n²−1)⁻¹ versus (hυ)² for the PVB/Sb₂O₃ nanocomposites.

Table 2.

The values of E₀, E_d, n_o, ε_s, ε_l, and N/m* for PVB/Sb₂O₃ nanocomposites.

Sample	E0 (eV)	Ed (eV)	no	εs	εl	N/m* (m−3 kg−3)	N (cm−3)
PVB +0% Sb2O3	4.41	3.53	1.340	1.80	1.83	2.1 ×1054	1.9 ×1018
PVB +1% Sb2O3	3.85	4.56	1.478	2.18	2.26	6.3 ×1054	5.7 ×1018
PVB +2% Sb2O3	3.60	4.92	1.538	2.36	2.46	7.8 ×1054	7.1 ×1018
PVB +3% Sb2O3	3.39	5.36	1.606	2.58	2.68	10.5 ×1054	9.6 ×1018

The formula shown below may be used to express the real component of the dielectric constant, denoted by ε_r ⁴⁸ :

${\mathbf{\epsilon }}_{\mathit{r}}={\hspace{0.17em}{\mathit{n}}^{\mathbf{2}}-{\mathit{k}}^{\mathbf{2}}=\mathit{\epsilon }}_{\mathit{l}}-\left(\frac{{\mathit{e}}^{\mathbf{2}}}{\mathbf{4}\hspace{0.17em}{{\mathit{\pi }}^{\mathbf{2}}{\mathit{\epsilon }}_{\mathit{s}}\mathit{c}}^{\mathbf{2}}\hspace{0.17em}}\frac{\mathit{N}}{{\mathit{m}}^{*}}\right){\mathit{\lambda }}^{\mathbf{2}}$

(7)

Where ɛ_L and N/m* are the lattice dielectric constant and the ratio of the concentration of free carrier ions to the effective mass, respectively. By calculating the intercept and slope of the linear portion in the plots of ε_r against λ², as seen in Figure 11, it is possible to determine these characteristics. The lattice dielectric constant ε_l improved from 1.83 to 2.68 as the concentration of Sb₂O₃ increased. The N/m* value is 2.1 × 10 ⁵⁴ kg⁻¹ m² for PVB. On the other hand, the N/m* value increases to 10.5 × 10 ⁵⁴ kg⁻¹ m⁻³ for PVC/3 wt%Sb₂O₃ nanocomposite (Table 2). These changes demonstrated that the interaction between PVB and nanofiller increased the concentration of free carriers.

Figure 11.

ε_r versus λ² for the PVB/Sb₂O₃ nanocomposites.

The formula may be used to determine the connection between the imaginary dielectric constant ( ε _i ) and λ³ (Figure 12) can be written as follows ⁴⁹ :

${\mathit{\epsilon }}_{\mathit{i}}=\frac{\mathbf{1}}{\mathbf{8}{\mathit{\pi }}^{\mathbf{3}}{\mathit{\epsilon }}_{\mathbf{o}}}\left(\frac{{\mathit{e}}^{\mathbf{2}}}{{\mathit{c}}^{\mathbf{3}}}\right)\left(\frac{\mathit{N}}{\mathit{m}*}\right)\frac{\mathbf{1}}{\mathit{\tau }}{\mathit{\lambda }}^{\mathbf{3}}$

(8)

Figure 12.

The correlation between ε _i versus λ³ for the PVB/Sb₂O₃ nanocomposites.

Here, τ stands for the relaxation time of electrons. As a result, the relaxation time values for the PVB/Sb₂O₃ nanocomposites were obtained from the slope of the ε_i and λ³ and provided in Table 3. The relaxation time clearly decreases once the Sb₂O₃ is embedded. The outcomes showed that the Sb₂O₃-doped PVB is more suitable for optoelectronic devices compared to the pure film.

Table 3.

Optoelectrical parameters for PVB/ Sb₂O₃ nanocomposites.

Sample	τ (s)	ωp (Hz)	μopt. (c.s.kg−1)	ρopt. (c−2.s−1kg–1 m3)
PVB +0% Sb2O3	2.0 × 10−16	1.2 × 1014	0.000035	9.39 × 10−2
PVB +1% Sb2O3	2.18 × 10−16	2.1 × 1014	0.000038	2.89 × 10−2
PVB +2% Sb2O3	1.80 × 10−16	2.55 × 1014	0.000031	2.58 × 10−2
PVB +3% Sb2O3	1.5 × 10−16	3.12 × 1014	0.000026	2.50 × 10−2

The real component of the dielectric constant (ε_r) can be used to estimate the oscillation frequency (ω_P) for PVB/Sb₂O₃ nanocomposites with varying Sb₂O₃ percentages (0, 1, 2, and 3 wt%) employing the formula listed below ⁵⁰ :

${\mathit{\epsilon }}_{\mathit{r}}={\mathit{\epsilon }}_{\mathit{h}\mathit{f}}-\frac{{\mathit{\omega }}_{\mathit{P}}^{\mathbf{2}}}{{\mathit{\omega }}^{\mathbf{2}\hspace{0.17em}}}$

(9)

where ε _hf is the dielectric constant at high frequency.

The relationship between ε_r and ω⁻² has been demonstrated in Figure 13, which illustrates the interaction through PVB/Sb₂O₃ nanocomposites with varying Sb₂O₃ percentages (0, 1, 2, and 3 wt%). The values of ω_p for nanocomposites were obtained by calculating the slope of those straight lines and are shown in Table 3. Increasing the amount of Sb₂O₃ results in a rise in the refractive index and polarisation, which in turn leads to significant fluctuations in the values of ε_r. Through the addition of Sb₂O₃, the change in ω_p for PVB/Sb₂O₃ nanocomposites is influenced by the increase in the concentration of free carriers. As the percentage of Sb₂O₃ rises, the oscillation frequency value falls within the range of 1.2 × 10¹⁴ to 3.12 × 10¹⁴ Hz.

Figure 13.

The correlation amongst ε_r and ω⁻² for PVB/Sb₂O₃ nanocomposites.

The optical mobility (µ_opt.), and the optical resistivity ( ρ _opt ) for PVB/Sb₂O₃ nanocomposites can be determined as follows^51,52:

${\mathit{\mu }}_{\mathit{o}\mathit{p}\mathit{t}}=\frac{\mathit{e}\mathit{\tau }}{\mathit{m}*}$

(10)

${\mathit{\rho }}_{\mathit{o}\mathit{p}\mathit{t}}=\frac{\mathbf{1}}{\mathit{e}{\mathit{\mu }}_{\mathit{o}\mathit{p}\mathit{t}}\mathit{N}}$

(11)

The optical mobility for PVB/Sb₂O₃ nanocomposites ranged between 26 × 10⁻⁶ c.s.kg⁻¹ and 38 × 10⁻⁶ c.s.kg⁻¹. Conversely, the optical resistivity decreased from 9.39 × 10⁻² to 2.50 × 10⁻² c⁻².s⁻¹.kg⁻¹.m³, as seen in Table 3. The phenomenon arises when the bandgap diminishes, hence promoting increased conductivity as electrons may rapidly transition from the valence band to the conduction band. ⁵³ The optoelectrical parameters have been studied in many previous literatures.^54,55 Suwannakham et al., ⁵⁴ reported that the oscillation frequency value falls within the range of 6.67 × 10¹⁴ to 8.22 × 10¹⁴ Hz, and the optical resistivity ranged between 7.2 × 10⁻² to 2.152 c⁻².s⁻¹.kg⁻¹.m³ for antimony-doped tin oxide thin films.

Conclusion

XRD revealed that the interaction of Sb₂O₃ with PVB results in an increase in the crystallinity of the nanocomposites. Furthermore, the FTIR confirmed the interaction between PVB and nanofiller. The transmission spectra of the PVB/Sb₂O₃ nanocomposites declined upon increasing the Sb₂O₃ NPs ratios inside the polymeric matrix. The absorption coefficient increased with the rise of photon energy within the visible to near-infrared (NIR) spectrum and exhibited a significant increase in the ultraviolet region. The structural disorder caused by nanofiller decreases the optical band gap and increases Urbach energy inside nanocomposites. The incorporation of Sb₂O₃ NPs results in an increase in the values of the refractive index and extinction coefficient, which can be attributed to modifications to the PVB matrix. Additionally, the values of _Ed., n₀, and ε_s increased with the addition of nanofiller. In contrast, E_o declined, indicating a rise in charge transfer between Sb₂O₃ and PVB, accompanied by an increase in disorder in the PVB. Lattice dielectric constant ε_l improved from 1.83 to 2.68 as the concentration of Sb₂O₃ increased. The N/m* value is increased from 2.1 × 10 54 kg⁻¹ m to 10.5 × 10 54 kg⁻¹ m⁻¹ with increasing Sb₂O₃ up to 3 wt%. The relaxation time and oscillation frequency values decrease once Sb₂O₃ is embedded. The outcome confirms that Sb₂O₃ can modulate the optical features of PVB, making it suitable for various applications, including UV shielding, optical fibers, anti-reflective coatings, and optoelectronic devices.